Point-to-multipoint localized distribution systems are known in the art. Typical systems use multiple low power node antennas, also commonly referred to as cell stations, base stations, and hub stations; which deliver wireless communication services to receiving stations in an area of coverage, e.g., “cell”, defined around the node antennas. The node antennas are arranged to form partially overlapping cells. Frequency differentiation, polarization differentiation and similar techniques are used alone or in combination to prevent conflicting signals from adversely affecting communications received by receiving stations at or- near areas of overlap between adjacent node antennas and between adjacent sectors of a particular node antenna.
An interesting point-to-multipoint microwave television distribution system utilizes devices in the millimeter wave frequency band, between about 28 GHz and 300 GHz. Of particular interest is the 29 GHz band, from 27.5 to 31.3 GHz, which provides sufficient width to accommodate a number of broadband channels, avoids previously allocated terrestrial bands, avoids satellite down-link bands, permits relatively small sized antennas, and is compatible with known low-cost microwave circuit fabrication techniques.
In such a LMDS, a low power microwave base station communicates with a plurality of subscriber stations in its transmission cell. Multiple base stations are arranged in an array to extend coverage beyond a single cell. LMDS telephony and data communications from a base station typically communicate with subscriber customer premise equipment located within about 5 kilometers of the LMDS base station. Establishing and maintaining communications with customer premise equipment i.e., all equipment in customer premises connected through the LMDS wireless link, such as RF Network Interface Unit (NIU), telephones, computers, PBXs, etc., requires allocation of channels and time slots for communication of data and control information. Efficient use of available bandwidth is best realized through a dynamic frequency assignment since having fixed frequencies for particular CPE will often leave significant unused bandwidth.
Three general problems are encountered with such dynamic assignment. First, a downstream channel must be dynamically assigned to a customer premises NIU. In addition, an upstream channel and time slot must be dynamically assigned to a customer premises NIU. Finally, a manner for a customer premise to request either downstream or upstream frequency assignment must be provided.
This dynamic LMDS assignment problem remains essentially unaddressed in conventional LMDS. Mobile telephone cellular systems have one or more frequencies dedicated for requesting a downstream control frequency. This dedicated downstream frequency is separate from the data frequencies used to carry voice payload. This approach has little value for LMDS, which is based on assigning a single downstream frequency to a customer premises, with several customer premises sharing the same upstream frequency for control and transferring of telephony and data information. A further difference is that LMDS supports trunk line service while cellular does not. LMDS accordingly has a unique set of requirements for performing both dynamic downstream and upstream frequency assignment, believed to be unaddressed in known prior art techniques.
Thus, there is a need for an improved localized microwave distribution system that provides for dynamic downstream and upstream frequency assignment. It is an object of the invention to provide such an improved system.
It is a further object of the invention to provide an improved localized microwave distribution system including a method and protocol for dynamically allocating customer premise equipment to a downstream frequency based upon periodic message assignments retrieved through a scan of home common control channels.
An additional object of the invention is to provide an improved localized microwave distribution system including a method and protocol for dynamically allocating customer premise equipment to a downstream frequency via a request for downstream frequency assignment.
Another object of the invention is to provide an improved localized microwave distribution system including a method and protocol for dynamically allocating an upstream frequency and time slot to customer premise equipment.
Still another object of the invention is to provide an improved localized microwave distribution system including a method and frequency contention protocol for competing customer premise equipment to pick a common control channel for communicating either a downstream or upstream frequency request or time slot request to a base station.
A still further object of the invention is to provide an improved method and protocol for upstream burst mode applications which require upstream frequency assignment.